Power consumption is an important issue in battery powered electronic circuits, generally. In the automotive industry, a great emphasis has been placed on extending the life span of batteries. This issue, when taken in combination with the increasing number of electrical and electronic content and complexity within present automobiles, presents a unique dilemma.
A solution for simplifying the management of this electrical and electronic content which has gained increasing acceptance within the automotive industry has been multiplexing. Multiplexing proposes to electrically couple each electrical and electronic device through a singular loop interface with a microcontroller.
Managing each electrical and electronic device constantly is wasteful and inefficient. Thus, in attempting to balance the interests of power savings against the benefits of multiplexing, one solution proposed has been to allow the microcontroller to operate in a sleep mode of operation during all times when the microcontroller processing capabilities are not required.
Referring to FIG. 1, a multiplexed control system 10 is illustrated having reduced power consumption. System 10 comprises a microcontroller 20 for controlling first and second electronic devices 24 and 28, respectively, by way of first and second control switches 12 and 14. Control switches 12 and 14 are coupled to one another, and through a singular loop, also coupled with microcontroller 20.
To effectively realize a multiplexed architecture, first and second devices 24 and 28 are also coupled to each other, and through a singular line, coupled with microcontroller 20 as well as ground. By this configuration, microcontroller 20 processes effective changes in the status of each switch by feeding a device control signal through the multiplexed input loop.
System 10 additionally comprises one diode for each switch. First and a second diode, D.sub.1 and D.sub.2, provide a means for detecting a change in the status of each respective control switch, 12 and 14. Diodes, D.sub.1 and D.sub.2, are each coupled with the interrupt sensor of microcontroller 20. By this design, each diode independently enables microcontroller 20 to effectively wake up from a low power sleep mode when it is not required to a fully powered active mode when its processing capabilities are required.
System 10 of the FIG. 1 poses a substantial shortcoming. In automobiles having a greater number of electrically powered devices, a diode is required for each device to enable the microcontroller to switch from sleep mode to active mode. Further, in manufacturing a large number of systems, this can be fairly costly.
Thus, a demand exists for a multiplexed system having a power consumption savings that is substantially more cost effective than the known art.